I can't login to virtualmin from other subnet

i install virtualmin on centos 6.5.but i can login to server (https://virtualmin_ip_address:10000) only from PCs that the IP address is in the same subnet of virtualmin
virtualmin IP address:x.x.38.20/
then i can login only from pc that IP is in this range: x.x.38.1-x.x.38.30 ( subnet:
what is problem?

I am guessing your issue is related to a workplace firewall. If you are trying to access your server in a workplace, I would suggest talking to someone that knows how the firewalls and routers are configured.